Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 19 | Moderate
24 Piece hasWon(Piece[][] board) {
25 int N = board.length;
26 Piece winner = Piece.Empty;
27
28 // Check rows and columns
29 for (int i = 0; i < N; i++) {
30 winner = getWinner(board, i, Check.Row);
31 if (winner != Piece.Empty) {
32 return winner;
33 }
34
35 winner = getWinner(board, i, Check.Column);
36 if (winner != Piece.Empty) {
37 return winner;
38 }
39 }
40
41 winner = getWinner(board, -1, Check.Diagonal);
42 if (winner != Piece.Empty) {
43 return winner;
44 }
45
46 // Check diagonal
47 winner = getWinner(board, -1, Check.ReverseDiagonal);
48 if (winner != Piece.Empty) {
49 return winner;
50 }
51
52 return Piece.Empty;
53 }
SUGGESTIONS AND OBSERVATIONS:
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Note that the runtime could be reduced to O(N) with the addition of row and column
count arrays (and two sums for the diagonals)
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A common follow up (or tweak) to this question is to write this code for an NxN board.
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Cracking the Coding Interview | Additional Review Problems